Amperage is relavent at low voltages. Things work on either
extremely high voltages _or_ medium to high currents. It's all a
matter of the energy involved. I think the trick in the case of the
electret is one of getting that high voltage to do work- which isn't
easy because we've NOT come up with a decent HV equivalent of our low
voltage (and even tubes are low voltage in most cases at 50Kv)
technology.
-- Frank Earl